TANGO scientific expeditions

We have just released the TANGO2 expedition report. The report will give you an overview of the activities of the TANGO2 team in the West Antarctic Peninsula, onboard RV Australis.

The TANGO2 expedition ventured to accumulate new information and samples to delineate responses of marine ecosystems to shifts in ice regimes in the West Antarctic Peninsula (WAP), taking full advantage of a nimble sampling platform, the R/V Australis, a steel hulled, fully rigged motor sailor. TANGO2 took place between February and March 2024, sampling three main locations at different spatial scales. Deploying 11 different types of gear (both traditional and modern), the TANGO2 Team gathered over 4000 physical samples that will be brought back to Belgium for further analysis. The Team focused on synchronized, transdisciplinary sampling to understand the linkages between realms (atmosphere, water column, seafloor) and there potential responses to changes in climate- changed linked ice regime at various spatial scales.
Once more, the use of R/V Australis for coastal studies deemed to be extremely efficient, in terms of environmental impact (ca. 40 times less CO2 emissions than a Polar class icebreaker) and agility, allowing the Team to adapt the sampling efforts in function of the weather or anchoring conditions. Fully devoted to the expedition, the ship allowed the TANGO2 team to sample in shallow areas, not accessible to icebreakers and too far away from research stations, and which have been under sampled (based on data available from the reference information system for Antarctic marine biodiversity data, biodiversity.aq). The preliminary (meta)results accumulated during TANGO2 confirm the efficiency of using a nimble research platform to study fine-scale processes in the shallow areas of unchartered regions of the West Antarctic Peninsula. TANGO2 provides a first-hand experience to carry an future expeditions taking advantage of the low cost/low environmental impact approach, coherent with environmental conservation. Based upon Open Science approach, the combination of B121/TANGO1 and now TANGO2 efficiency in designing informed, focused expeditions, paving the way to transposing the concept developed by Danis et al. (2022) to multiply similar efforts in a coordinated fashion.
An overview of initial results is provided below:

1. Concept and Sampling design
   The preliminary (meta)results accumulated during TANGO2 confirm again the efficiency of using a nimble research platform to study fine-scale processes in the shallow areas of unchartered regions of the West Antarctic Peninsula. Based upon Open Science approaches, the concept tested and improved during the B121/TANGO1/TANGO2 paves the way to transposing the concept, and to multiply/coordinate similar efforts in different oceans.
2. Mapping
   Despite being rather sensitive to environmental conditions (strong wind velocity, compass interference with vessel, takeoff/landing delicate from vessel), deployment of drones was found to be useful in terms of scouting when arriving in new work sites, documenting their general setup as well as carrying out more sophisticated works including orthomosaic (2D) and photogrammetry (3D).
3. Environmental parameters
   A total of six incubations were performed at every substation. There was no visible difference between the stations or the bottle during the filtration. Sediment traps were deployed successfully after coordinated recovery of the sample bottle and release by divers and
   surface recovery. There was less matter compared to TANGO 1 expedition but the sediments seems bigger and more stringy. The three sites seem to have a comparable quantity of particulate matter.
   A total of 123 Niskin bottles were taken at the surface. These samples were taken in various environment, including active glaciers, open water and coastal environment without glacier. These samples were taken following the results of the TANGO1 expedition. It showed a potential source of methane at the top of the water column. The hypothesis is that this source come from run-off water from the glacier.
   The sampling strategy of TANGO2 have been adapted to this hypothesis to sample sensitive area as glacier with a high velocity. This was done to assess the impact of melting glacier as a source of methane in the West Antarctic Peninsula.
4. Biogeochemistry
   To determine the quantity and distribution of carbon present in the seafloor sediment from different sources, divers pushed 3 perspex cores into the seafloor sediment at each site, aiming for a sediment column of at least 10 cm. After retrieval, the cores were sliced and all samples were immediately stored into a -20 °C freezer.
   Two types of incubations were performed: dark incubations, and light incubations, representing the light intensity on the seafloor on a partially overcast day (as measured with HOBO loggers (Scaled instruments) on CTD profiles). Oxygen consumption rates measured in the dark incubations were similar for all the investigated sites, with average rates varying around 20 mmol O2 m-2 d-1. The exception was one of the sediment cores collected next to the wreck of the Guvernøren (Føyn harbor), which had more than double the oxygen consumption as most of the other stations
5. Trophic analysis
   A total of 2259 samples were collected, accounting for 101 different morphospecies sampled in the 6 stations investigated. Samples collected during TANGO2 would enable to refine thjose obtained during TANGO1 and extend the spatial range of study. Indeed, for instance, N. concinna, was found in every station. This will allow comparison of rock habitat among a range of latitude but also compare potential diet differences between rock and soft sediment habitats. Biometry measurements were also taken.
   Sampling was performed to characterize gut microsymbionts from sea urchins (Sterechinus neumayeri). The samples will be analysed using different methods: The samples preserved dried (Aristotle’s lantern) will be analysed in ULiège once return in Belgium for trophic niche analyses, The food pellets and gut epithelium samples will be processed at ULB (DNA extraction and PCRs) and send to a sequencing company to assess the diet and microbiome composition. The gonads will be processed at ULB for sea urchin sexing, as well as in Germany for proteomics studies (MALDI-TOF), the spines will be used in Germany for genomics studies (RAD sequencing).
6. Biodiversity inventories
   All sample collected in the different events of Rauschert Dredge and the Amphipod Traps have been partially sorted by main morphotypes on board of RV Australis during the expedition. Representants of the major taxa present in the catch were isolated, identified to the lowest taxonomic level known and counted whenever time and space was available. All

sorted taxa and unsorted subsamples were labeled and fixed in ethanol to be processed further thoroughly in the laboratory.
Regarding Top Predators (Birds and Marine Mammals), a total of 64 observation events (standard counts or punctual observations) were performed while crossing the Magellanic Area (MA), the Drake Passage (DP) and along the Antarctic Peninsula (AP). General notes on the observations for each species encountered during the voyage were taken. Remarkably, very low densities of birds during both crossings of the Drake Passage were observed compared to similar crossings performed at similar dates during previous years. Several species, although normally common or frequently observed during such transect e.g., the Southern Royal Albatross (Diomedea epomophora), Snow Petrel (Pagodroma nivea), White- headed Petrel (Pterodroma lessonii), Antarctic Petrel (Thalassoica antarctica), Kerguelen Petrel (Lugensa brevirostris) or Blue petrel (Halobaena caerulea) were absent during this voyage.

During the Tango 1 expedition, an important part of the projects relies on samples and data collected by SCUBA divers. Our diving team is composed of Francesca (UGent), Martin (ULiège), Lea and Camille (ULB).

Antarctic waters are a first for all members but Francesca, and previous training was an important part in the planning of the expedition. First, all divers needed to obtain a European Scientific Diver certification to be able to carry on research underwater. The team then trained in Belgium using the same tools they would use here, around the Antarctic Peninsula.

Diving in Antarctica mainly requires the ability to cope with freezing-cold water. For this, the dry suit is a must and is completed by multiple layers of thermal underwear and warming equipment. Luckily, Belgian weather can offer extreme diving conditions, with quarries and lakes reaching down to 4°C during the winter. Our team was therefore well prepared and did not suffer from more than a few cold fingers.

On-site they collect specimens, sediments cores along with pictures and videos to document the expedition.

The Team is leaving tomorrow for the first expedition of the TANGO project, to the Grandidier Channel, in the West Antarctic Peninsula, onboard the RV Australis (A motor sailboat operated by Ocean Expeditions, Capt. Ben Wallis).

TANGO1 is about understanding ecosystems responses to climate change in the Southern Ocean, and in particular trying to identify tipping points (at which ecosystems can drastically change in terms of structure and function) using a holistic scientific design.

TANGO1 is about exploring areas which are poorly documented, understood and inventorized, in an informed fashion and yet are undergoing accelerating environmental pressure.

TANGO1 is about coherence in terms of environmental impact. We want to lead by example, as we use a sailboat to carry marine science work in an extreme environment. RV Australis will allow us to reach particularly low levels of GHG emissions and habitat disturbance during sampling operations.

TANGO1 is about agility. Our sailboat allows us to reach shallow areas, and make fast decisions as we adapt to the conditions we will be meeting in the field.

TANGO1 is about commitment. We pledge to be in complete immersion in the environment we will be studying as we are convinced this will contribute to raise awareness about the importance of nature conservation.

We are leaving tomorrow, crossing the Drake Passage to the Western Antarctic Peninsula for a month of fieldwork.

After a full year of training, I am very excited to bring the ROV to Antarctica and finally explore the Southern Ocean seafloor.

When buying the BlueROV2 last year, we had no idea how much technical problems we would encounter. After 3 pool sessions (thanks to the David Lloyd and our dear Fabienne), multiple sessions in the “Vrouwenpolder” and the “Spuikom” (with thanks to Watersport Ostende Spuikom), a trip to Chile, another to Corsica and a final dive in the quarry of Barges, I think we pretty much discovered all possible problems and fixed them, learned about best practices and of course the importance of making check-lists (and reading them before departure…).

Let’s hope everything goes well once we’re there!

Lea

When people ask me what I do for work, I reply “I am a marine biologist”.The excitement then brings about the second question “oh wow! What do you study?” and often this initial excitement is soon killed off by my second answer : “sediment and worms” 😉 but not always though, I still manage to convince people of how awesome my job is!  Yes, I am one of those scientists to whom sand can speak and who find delight exploring a hidden world which cannot be fathom by the eye, but it needs a microscope and lots of patience to be witnessed and discovered. I work with soft sediments and a size class of organisms that live in them known as MEIOFAUNA…animals – yes, animals : they are multicellular, have organs and “limbs” a bit like us but are super tiny and they pass through a mesh sieve of 1 mm!!. Since the beginning of our cruise B121 I have explored during my dives the shallow bottoms of each location we have been visiting seeking for sand and mud. I have set out to collect sediment either by means of cores (plexiglas tubes which use vacuum to bring back on land a perfectly intact piece of the sea bottom!) or simply by scooping the surface of the sea bottom where sediment patches could be found.  What do I wish to find out by looking at these communities? I want to see what is their overall biodiversity in between the different sites we study since there are many different animals that live in the sediments in that size range, and their presence or absence from one location can tell us a lot about the health of the sea bottoms, for instance about how well is the recycling potential of the sediments doing in relation to the glacier retreat activity. It sounds very scientific right? But at the end of the day, I am just a girl having fun underwater and playing with mud on the surface! Look at this picture of me and Ryan (first mate on board) setting up my outdoor laboratory in the back of the Australis where I was dedicated  a little space to where to make it dirty for a little while!​

Among the many research projects conducted during the B121 cruise, trophic ecology has taken an important place for divers and fish specialists all along the campaign. But what is it about ? Beyond the formal and bit severe words, trophic ecology can be simply and instinctively recapped by the famous idiom “you are what you eat” ! Every single piece of snack each of us ingests or drop of liquid we are happy to sip not only contributes to maintaining our whole body in good shape but also, and insidiously leaves its indelible mark in our organs. This holds true for all living beings and for isotopes as well ! Analyzing the composition of organisms in Carbon, Nitrogen and Sulfur stable isotopes can tell us a lot about the long story of what they usually eat and where they have been living. Eventually, analyzing the isopotic composition of organisms living in close vicinity to each other in a same place can help unreveal biological interactions between them in the food chain that is, who’s eating whom and what. That’s why specimens of some common and key species of the visited sites were sampled at the sea bottom, from seaweeds to sponges, worms, starfish, sea urchins and fish, to caracterize main food web elements and compare them between sites. The complexity of food webs is also a condition of ecosystem resilience facing climate change, the more redundant and complex biotic interactions are in a food web and the more likely the ecosystem is to resist to change. Let’s wait a bit and see what isotopes will tell … !

Thomas

Alongside the numerous samplings done every day during the expedition, a timeframe is also dedicated to macro-photography. There, a different world can be revealed from what we cannot see with our poor human eyes…

“Wow, this little guy was a flatworm and not a leech“ or “Hey, look at this structure on the right, it is key for the identification “ are just two examples of B121 exclamations associated to someone looking at a macro-picture. 

That’s the key advantage of macro-photography: it gives you precious information to identify the organisms onboard (or after the expedition). Last but not least, this is also a good resource for future scientific publications and outreach activities.

That’s why Quentin (Jossart) is spending few hours every day to capture the most common or interesting species collected throughout the day. Photographing them alive is an asset because some structures or colors can deteriorate after preservation. A lot of patience is thus sometimes needed as some animals are constantly moving… “Please mate, stay here a seecccooonnddd” is the most polite exclamation that has been heard from the dedicated photo-area onboard.